PUMP HAVING ELECTROACTIVE POLYMERS AND A RETURN ELEMENT

Abstract

The present invention relates to a pump, comprising a pump actuator (2) having at least one electroactive polymer, as well as at least one return element (8, 9) which returns a displacement element (5) of the pump after a pump stroke to a defined position. The invention further relates to a metering unit and to a medical apparatus comprising such a pump.

Claims

1. A pump (1) for a medical device, in particular a blood treatment device, preferably a dialysis machine, comprising a pump actuator having at least one electroactive polymer, wherein the pump actuator has a trigger element, a displacement element, and a return element, with the return element being configured such that the displacement element can be moved to a defined position after an actuation of the trigger element.

2. A pump (1) in accordance with claim 1, characterized in that the return element has at least one spring, one magnet (8, 9, 13, 14), or one capacitor and the return element brings the trigger element into a defined position that is a pump position or the return element brings the trigger element into a defined position that is opposite to the pump position.

3. A pump (1) in accordance with claim 1, characterized in that the pump actuator, preferably the displacement element and/or the trigger element, has a plurality of layers, preferably a stack (2), of electroactive polymers, in particular dielectric electroactive polymers.

4. A pump (1) in accordance with claim 1, wherein the pump actuator has electrodes arranged in ring form, respectively having a silicone layer that is disposed between the electrodes and that are preferably configured as the trigger element.

5. A pump (1) in accordance with claim 1, characterized in that the pump actuator has a membrane (5) and the displacement element has a plurality of layers, preferably a stack (2), of electroactive polymers, and the membrane (5) can be moved from a starting position into a pump position by means of the electroactive polymers.

6. A pump (1) in accordance with claim 1, wherein the trigger element has a plurality of layers, preferably a stack (2), of electroactive polymers or electrodes arranged in ring form, respectively having a silicone layer disposed between the electrodes.

7. A pump (1) in accordance with claim 1, wherein the displacement element and/or the return element and/or the trigger element are formed as one element in part.

8. A pump (1) in accordance with claim 1, characterized in that the return element has one or more magnets and the at least one magnet (8, 9, 13, 14) has at least 8 individual poles, preferably more than 10 individual poles, even more preferably more than 14 individual poles.

9. A pump (1) in accordance with claim 1, characterized in that the return element comprises at least one capacitor, with the capacitor being charged by the released energy on a dilatation of the electroactive polymer and with the released energy being able to be used for a contraction of the electroactive polymer on a discharge of the capacitor.

10. A pump cabin (1) in accordance with claim 1, wherein the return element is at least one capacitor, the trigger element is an electroactive polymer, and the displacement element is at least one spring, at least one magnet, or at least one capacitor, each being connected to a movable membrane (5), preferably further comprising an electric energy storage device that can store the energy of the capacitor and/or of the dielectric elastomer.

11. A metering unit, in particular a metering unit for a blood treatment device, having a pump (1) in accordance with claim 1.

12. A medical device, in particular a blood treatment machine, having a pump (1) and/or a metering unit in accordance with claim 1.

13. Use of a pump (1) in accordance with claim 1 in a medical device, in particular a blood treatment apparatus, preferably a dialysis machine.

14. A method of pumping fluid for a medical device, in particular a blood treatment apparatus, in particular a dialysis machine, having a pump (1) in accordance with claim 1, wherein the pump (1) has a pump space for conveying fluid, comprising triggering the trigger element by changing an electric voltage; moving the displacement element from a starting position into a pump position so that fluid is displaced from a pump space; and returning the displacement element from the pump position into the starting position or returning the displacement element into the pump position after leaving the starting position.

15. A method in accordance with claim 1, wherein the return element has a capacitor; and wherein the triggering of the trigger element takes place by a discharge of the capacitor and a return of the displacement element takes place by a charging of the capacitor; and/or wherein at least a portion of the electrical charge or energy of the capacitor flows between the return element and the displacement element.

Description

[0094] Further features, advantages, and effects of the present invention result from the following description of preferred embodiments of the invention with reference to the associated Figures in which similar or the same components are marked by the same reference numerals.

[0095] There are shown:

[0096] FIG. 1 a schematic drawing of an embodiment of a pump in accordance with the invention;

[0097] FIG. 1a a schematic drawing of a different embodiment of a pump in accordance with the invention;

[0098] FIG. 1b a schematic drawing of a further embodiment of a pump in accordance with the invention;

[0099] FIG. 2a flowchart that illustrates the use of pumps in accordance with the invention as part of an embodiment of a blood treatment machine;

[0100] FIG. 3 the embodiment of FIG. 2 with multiway valves instead of standard valves;

[0101] FIG. 3a an embodiment with an additional balance chamber;

[0102] FIG. 4a flowchart that illustrates the use of pumps in accordance with the invention as part of a different embodiment of a blood treatment machine;

[0103] FIG. 5 shows the embodiment of FIG. 4 with multiway valves instead of standard valves;

[0104] FIG. 6 a flowchart that illustrates the use of pumps in accordance with the invention as part of a different embodiment of a blood treatment machine;

[0105] FIG. 7 snows the embodiment of FIG. 6 with multiway valves instead of standard valves;

[0106] FIG. 8 shows an embodiment of a further pump in accordance with the invention; and

[0107] FIG. 9 shows an embodiment of a different pump in accordance with the invention.

[0108] The pump 1 shown in FIG. 1 has three stacks 2 of electroactive polymers arranged next to one another. The pressure generated by the stacks 2 of electroactive polymers is transmitted via a common connection plate 3 to a force bundling structure 4 whose area is smaller than the area of the connection plate 3. The pump shown in FIG. 1 can be used as a valve 1.

[0109] The force bundling structure 4 is connected to a pump membrane 5 that is moved up and down in accordance with the deformation of the stacks 2 of electroactive polymers. The longitudinal direction of the stacks 2 of electroactive polymers and the direction of the deformation of the stacks 2 are thus aligned in parallel with the direction of the pump strokes of the pump 1. In an optional variant, the force bundling structure 4 can also be designed as a stack of electroactive polymers. In this variant, however, it does not serve as an actuator that generates the stroke movement of the pump. This separate stack of electroactive polymers rather serves the more accurate self sensing of the stroke movement. For the force bundling, the electroactive polymer particularly advantageously here has a greater hardness or smaller elasticity than the electroactive polymers used for the stroke movement. An optional processing unit can more accurately determine the stroke that actually took place and the force that acts on the membrane in the stroke direction using the electrical measurements of the capacitances or potentials of all the electroactive polymers of the device.

[0110] The pump shown in FIG. 1 a additionally has a return element having two magnets 8, 9. The magnet 8 is installed at an upper element of the pump housing 10 or at the top of the pump chamber and the magnet 9 is connected to the pump membrane 5. It is ensured by the attraction force of the magnets 8, 9 that the membrane 5 is moved completely up to the upper abutment (top of the pump chamber) on every pump stroke. The conveying medium of the pump 1 flows into the pump chamber via an inlet 11 and exits the pump chamber via an outlet 12. In an alternative variant, the return element is alternatively or additionally designed as an electric capacitor having two capacitor plates 8, 9. It is achieved or facilitated by the electrostatic attraction of the plates to one another when the capacitor has a charge that the membrane 5 reaches the upper abutment of the pump. In this variant, monitoring can particularly advantageously be carried out by a monitoring of the electrical properties of the return element designed as a capacitor. If the membrane 5 is at the upper end abutment of the pump, a specific, known capacitance of the return element designed as a capacitor is adopted. The reaching of the end abutment can therefore be determined by the measurement of the capacitance or of other electrical properties (saturation current, impedance, saturation potential). A particularly precise pump can thereby be provided that yet further improves the high precision and measurement of the pump strokes by means of self sensing.

[0111] As shown in FIG. 1b, the magnets 8 and 13 interacting with the pump membrane 5 can also be installed at different locations on the pump housing 10. In the embodiment shown in FIG. 1b, the magnets 8 and 13 are installed at both sides in the side walls of the pump housing 10 close to a base of the pump chamber. In an alternative variant analog to the alternative described in connection with FIG. 1a, capacitor plates are provided instead of magnets or in addition to magnets so that a return element alternatively or additionally comprises one or more electric capacitors.

[0112] In FIG. 2 a flowchart is shown that illustrates the use of pumps in accordance with the invention as part of a blood treatment machine;

[0113] Dialysis is a process for blood purification that is used in patients who are affected by renal failure. Their kidneys are no longer able to filter toxins produced by the body from the blood. Further important processes in the regulation of the water and electrolyte metabolism of the patients are furthermore impaired.

[0114] To remove the toxins, the patient's blood is brought into contact with dialysis liquid via semipermeable hollow fiber membranes in a dialyzer. Substances, specifically toxins, electrolytes, and proteins, can diffuse to and fro between the liquids through this membrane. Since diffusion is a process driven by concentration and should prevent foreign bodies from diffusing into the patient's blood, the dialysis liquid, the so-called dialyzate, consists of ultrapure water.

[0115] Additional concentrates such as electrolyte concentrates and bicarbonate are additionally metered into the dialyzate to balance the electrolyte metabolism of the patient. This is conventionally done via the pumps P05 and P06 that are replaced by the present invention so that the pumps P05 and P06 are struck out in the Figures.

[0116] In a conventional blood treatment machine, the dialysis water is conveyed in the direction of the balancing chamber H14 by a pump via a heating chamber and an air separator. In addition to the dialysis water, acids and bases are added to the water and together form a physiological solution via the pumps P05 (concentrate pump) and P06 (bicarbonate pump).

[0117] It is technically ensured in the balancing chamber that the same amount of physiological solution is conveyed to the patient as liquid comes from the patient. An additional dialysis liquid filter F04 having a dead volume of e.g. approximately 300 ml is arranged between the balancing chamber and the dialyzer. This dead volume is relevant to the observation of flow peaks and their smoothing; this dead volume further acts as a kind of fluid store.

[0118] The physiological solution reaches the dialyzer, where it is used to purify the blood, from the dialysis liquid filter F04. After the purification of the blood, the dialysis liquid is again introduced into the balancing chamber H14 via a pump and finally enters into the drain.

[0119] In addition, an ultrafiltration pump P04 (UF pump) is installed in most blood treatment machines. It should remove additional water from the patient. The ultrafiltration pump is decoupled from the balancing by means of the balancing chamber H14 since it performs a targeted water removal that should not be corrected.

[0120] The concentrate and the bicarbonate are conventionally injected or metered into the line directly before the balancing chamber. A very high water pressure of approximately 1.8 bar is present at this position due to technical circumstances. This means that the pumps have to convey against this pressure, which represents a technical challenge.

[0121] An approach of a technical solution can thus comprise metering in downstream of the balancing chamber. A considerably smaller pressure is present after the balancing chamber.

[0122] A flowchart of an embodiment of the present invention is shown in FIGS. 2 and 3 in which both the concentrate and the bicarbonate are fed in by means of pumps in accordance with the invention (pumps having electroactive polymers, EAP pumps) after the balancing chamber H14 and directly before the dialysis liquid filter F04 that serve as a reservoir/mixing chamber.

[0123] A considerably smaller water pressure is present in this region than directly upstream of the balancing chamber H14. The volume is injected after or downstream of the balancing chamber (EAP pump 6 in the stored progression before/upstream of the patient “Before pat”) and is thus not considered in the balancing. The patient would thus be continuously subjected to excess water by the injected volume without any further measures. There is accordingly the necessity of removing this volume again.

[0124] This can be done either via the existing UF pump (P04) or via a further EAP pump (EAP pump 7 in the stored progression after/downstream of the patient “After pat”). Since the volume metered in by means of the EAP pump 6 is known, the same volume can easily be removed again.

[0125] The EAP pumps named here can be considered as volumetric metering systems. This means that a metering takes place in that a known pump space, that is a volume, is removed. Since the metered media are preferably liquids, that is are practically not compressible, the conveyed quantity—the dose—is clearly set by the volume or corresponds to the volume conveyed by a pump stroke or a specific number of pump strokes. In comparison with other methods of metering, the EAP pumps therefore bring about a higher reproduction accuracy as an intrinsic property, that is a higher accuracy on repeated procedures. To further improve this for the use of EAP pumps as metering and UF pumps here, a further balancing device 9 having a balancing chamber 9a that may be smaller van be interposed between the two pumps 5 and 6 and the line 8 into which metering takes place, as is shown schematically in FIG. 3a. In this embodiment, the dialyzer is marked by D, the patient by P, and the balancing device H14 comprises two balancing chambers 14a and 14b. In this further development, a check can be made redundantly by means of the balancing device 9 or the balancing chamber 9a that the metering by the EAP pumps was exact and increased safety can thereby be achieved. It is thus also ensured that exactly that metering volume is removed again that was previously added on the metering into the dialyzate circuit.

[0126] In embodiments in which a volumetric balancing chamber is arranged for the balancing of the metering between the metering pumps and the line into which the metering takes place, any other pumps can be used for the metering instead of EAP pumps such as peristaltic pumps, membrane pumps, gear pumps, centrifugal pumps—for example impeller pumps.

[0127] The properties (small strokes, high frequencies) of the pumps in accordance with the invention furthermore make it possible to combine different pump functions (e.g. the pumping of different solutions).

[0128] A blood treatment machine is thus generally conceivable in which a bicarbonate pump, a concentrate pump, and an ultrafiltration pump (UF pump) are designed as pumps in accordance with the invention. In this respect, the UF pump must be in a position to be able to remove both typical volumes to be removed and the metered electrolyte and bicarbonate volumes per treatment.

[0129] Alternatively, a single pump in accordance with the invention can also pump bicarbonate and concentrate and additionally a UF pump can be provided that is either a pump in accordance with the invention having electroactive polymers or is a conventional serial pump.

[0130] The functions of the pumping of bicarbonate and concentrate can also be combined in one pump in accordance with the invention; a UF pump and a balancing pump can additionally be provided that are each either a pump in accordance with the invention having electroactive polymers or a conventional serial pump. The object of the balancing pump in this respect comprises the removal of the volume added via the bicarbonate/concentrate pump. The UF pump therefore only has to convey the typical UF volume.

[0131] Alternatively, the functions of the bicarbonate pump, concentrate pump, and UF pump could also be combined in a single pump in accordance with the invention that is preferably present in the blood treatment device at least twice.

[0132] An embodiment will be explained in more detail by way of example in the following with respect to FIG. 4 or 5.

[0133] The EAP pumps 6 and 7 meter in concentrate and bicarbonate downstream of/after the balancing chamber H14, which enables an injection against a smaller pressure, and remove fluid for the balancing.

[0134] The first EAP pump 6 here takes over the metering/feeding of bicarbonate and concentrate, wherein, as shown in FIG. 5, it is possible to alternate between the two fluids by a multiway valve. The switchover of the fluids can also take place by regular valves (see FIG. 4). Since the metering/feeding takes place downstream of the balancing chamber, but upstream of the patient (see flow path “Before pat”), the fluid amount fed in has to be removed again to prevent an excess water supply to the patient. Fluid is therefore removed from the system after the patient (see flow path “After pat”), which is taken over by the second EAP pump 7. The original UF pump P04 remains in the system here.

[0135] In general, both pumps 6 and 7 can also take over both the feed and the removal of liquid.

[0136] A pump always has certain tolerances for technical production reasons and thus has a certain inaccuracy in the pumping of a defined volume. This has the result that, on the one hand, errors occur in the metering (metering errors) and in the removal of fluid. Considered overall, balancing defects thereby occur.

[0137] To balance these volume errors (metering and balancing errors) of the individual pumps, it is furthermore possible to interconnect the pumps via a valve circuit such that the functions of the pumps can be swapped by a switchover. This enables a compensation of the error. A control unit must be provided for this purpose that is adapted to correspondingly control the pumps.

[0138] In general, the EAP pump used or a plurality of EAP pumps used can be installed with the associated valves in a pump unit. In this respect, the metering pump(s) and the valves are preferably installed on one unit and can be operated by a central control. It can also include valves that are required for the feeding of fluids downstream of the balancing chamber.

[0139] It is possible by the use of a separate central control unit for the valves and the pump to operate the circuit of the pump unit completely separately from the control of a blood treatment machine. This separate control unit, for example, has its own CPU, which makes possible considerably shorter processing times in comparison with the use of the machine software. It is possible to reach higher pump frequencies by this reduced processing time.

[0140] It is thereby possible to utilize the specific characteristics of the EAPs (comparatively small stroke, but high frequency). In this respect, the desired conveying rate is necessary as the only input parameter on the machine software side; the required frequency and the required pump volume are then preferably calculated by the separate control unit.

[0141] A further embodiment of a blood treatment machine is shown in FIG. 6 that has a pump 6 in accordance with the invention and an ultrafiltration pump P04. The pump 6 in accordance with the invention pumps both concentrate and bicarbonate and the ultrafiltration pup P04 is preferably likewise designed as an EAP pump in accordance with the invention, but can also be a different kind of pump.

[0142] FIG. 8 shows a further pump in accordance with the invention. The pump has a housing 10 in whose upper abutment a polymagnet or a programmed magnet 8 has been placed. A further polymagnet or programmed magnet 9 is provided via the pump membrane 5 spaced apart from the polymagnet or programmed magnet, said further magnet 9 being connected to the housing of the pump via a COP electroactive polymer 15.

[0143] If the COP 15 is deformed, the polymagnet 9 is moved toward the polymagnet 8. If a specific distance between the polymagnets 8 and 9 has been reached, they repel one another and the polymagnets 8 and 9 move away from one another. The pump membrane 5 carries out this movement subsequently so that the pump membrane 5 is moved to convey medium by the deformation of the COP 15 and the movement of the polymagnets 8 and 9 toward and away from one another.

[0144] As shown in FIG. 9, a further polymagnet 14 can additionally be installed. The polymagnet 9 arranged between the polymagnets 8 and 14 is thus moved to and fro between the polymagnets 8 and 14, with the attraction or repulsion of the polymagnets having the effect that the polymagnet 9 reliably moves to and fro between an upper abutment and a lower abutment.